Best Of Arnold SW1 - what's inside (technical review)

[peteski]

For reference, here is a link to a discussion about which (non-sound, plug-n-play) decoder to use for this model.
https://www.therailwire.net/forum/index.php?topic=42498.0

[mmagliaro]

I picked up one of these Arnold SW-1's at a train show in February for a really good price (about $50).  It was too good to pass up.

Some observations. 

I changed out the traction tire wheels with all-metal wheels and it does make a big improvement in the spotty pickup.    6 wheels just aren't enough.   Traction tires give up 25% of the contact area on an 8-wheel engine, and that is huge. 

I did have to "roll my own" for the wheels.  I had a bunch of Kato diesel wheels lying around that were close to the right size and shape.  I had to turn two of them down by about .010" to match the Arnold ones, and then rebore the axle holes out to 1.5mm to fit the Arnold axles.   It took some doing.  But the results are definitely worth it.

As for pulling power, well, that's another story.  On level track, it's not bad.  It can pull about 11 40' freight cars (all 24g, all with Fox Valley wheels).  But up a 1.7% grade, it can barely manage 4 cars.  So keep that in mind if you want to get rid of the traction tires.  Like Peteski, I think reliable pickup is paramount so I am willing to give up the pulling power.  And since switchers spent their lives in yards that are likely to be level, performance on a grade probably isn't as important as it would be for a road engine.

Weight would help a lot.  This thing only weighs 43g.  That is super light.  If I can find some places to sneak in some Tungsten, I will.  Ideally, I'd like to add 15g, but I don't know if there's room for all that.

[peteski]

Weight would help a lot.  This thing only weighs 43g.  That is super light.  If I can find some places to sneak in some Tungsten, I will.  Ideally, I'd like to add 15g, but I don't know if there's room for all that.

Since you run DC, you can gut the electronics and hard-wire everything without the PC boards. It will be a bit of a pain to install the headlights, but I know you are more than capable of that challenge.     That will give you room to install more weight.

[mmagliaro]

Since you run DC, you can gut the electronics and hard-wire everything without the PC boards. It will be a bit of a pain to install the headlights, but I know you are more than capable of that challenge.     That will give you room to install more weight.

Thank you, sir!
But I am trying *not* to go this route.  I plopped a 15g weight on top of the engine and ran it.  The improvement is dramatic.  It could easily pull my 7-car test train up the hill, and more.  I don't know what it's limit is.  It also seems to run a little better - steadier.  I think the weight is helping with pickup, although not as much as with an axle point pickup system.  With axle points, extra weight bears down right on the contact surface between the point and the pickup cone in the side frame.  Since the Arnold uses back-of-the-wheel wipers, they aren't going to improve no matter how much weight is on the engine.  But the weight would help the wheels contact the rails better.

I working my way around the insides and the shell, sneaking tungsten cubes in wherever I can such that they won't interfere with disassembly and won't show.

Is that large rectangular fuel tank between the trucks an empty cavity inside?  Or is it solid frame metal?  Either way, I think it would be worth machining that out so I can stuff it with tungsten.  I would leave the outside borders of it alone so you would never see the difference.

[coosvalley]

I fit 1/8 tungsten cubes on either side of the couplers on the backside of the pilot(4 total), 5 in the cab, and two on the circuit boards, without any loco mods, besides the glue for the ones in the pilot.

[peteski]

Is that large rectangular fuel tank between the trucks an empty cavity inside?  Or is it solid frame metal?  Either way, I think it would be worth machining that out so I can stuff it with tungsten.  I would leave the outside borders of it alone so you would never see the difference.

Fuel tank is actually black-painted metal casting, integral with the rest of the chassis. Only the air tanks are add-on plastic parts.

[mmagliaro]

Well, I machined out the fuel tank area and filled it with tungsten plate.  Between that and adding tungsten behind the platform steps and on top of the circuit board (there is actually quite a bit of room for cubes on top of that board), I was able to get 15g of weight in there.  Runs nice.  Pulls well.  About 12 cars up the grade now, and that's plenty for me.

[peteski]

Well, I machined out the fuel tank area and filled it with tungsten plate.  Between that and adding tungsten behind the platform steps and on top of the circuit board (there is actually quite a bit of room for cubes on top of that board), I was able to get 15g of weight in there.  Runs nice.  Pulls well.  About 12 cars up the grade now, and that's plenty for me.

Excellent!

[towl1996]

Do any of you gentleman have a link to the tungsten cubes?  Thanks

[mmagliaro]

I used .076"  tungsten cubes (a little over 1/16") from here:
https://www.tungstenheavypowder.com/shopping/tungsten-balls-spheres-cubes/

It's a little expensive to buy a whole pound of them, but it's a great price when you realize how much you are getting compared to the Pinewood Derby shop prices, and I have never been able to find cubes this small anywhere else (the smallest I see on eBay or other sources are 1/8").

[Cajonpassfan]

That's a great resource, Max, thank you. With cubes this small, I suppose one can assemble lots of rectangular based shapes. I do have a stash of small circles, but find them inflexible and wasteful of space in most installations.
Could you please weigh one (or more) of these actual cubes? For example, what would a six by ten cube rectangle weigh? And are they consistent in size/thickness?
Thank you!
Otto K.

[Ed Kapuscinski]

Thinking about the non-TT wheels. These things are available pretty damned cheaply in a lot of places (kinda a bummer, actually). Are the wheel sets interchangeable?  If you can get one for ~$30 that gets you three good axles for $10 a piece.

[peteski]

Thinking about the non-TT wheels. These things are available pretty damned cheaply in a lot of places (kinda a bummer, actually). Are the wheel sets interchangeable?  If you can get one for ~$30 that gets you three good axles for $10 a piece.

There are 2 RT-equipped axles, so only 2 are usable per model.  As you can see the TT driver is non-insulated.  I  suppose you can try to pull off the insulated wheels off the axles to get more non-TT wheels, but they you will end up with axles which have both wheels insulated from the axle. I guess it doesn't really matter since the axle is not used for electric pickup.  But messing around with insulated wheels is asking for trouble (and for wobbly wheels).

[coosvalley]

I have swapped wheels around to get less TT axles. I bought a super cheap one, and used it for parts.  With some careful swapping, I ended up with 1 parts loco, 2 without any TTs, and 2 with just one TT per model, instead of 2. It isn't easy, but can be done.

These have definitely become my favorite N scale locos.

[peteski]

These have definitely become my favorite N scale locos.

Probably because they are ideal fit for your layout.    And they look good (except for the "treadplate" on the walkways. But unless you look close, you don't notice that.